Inner seal for a camshaft adjusting device in an internal combustion engine, specially a blade cell adjusting device

ABSTRACT

An internal sealing of a vane-type adjusting device comprising a drive pinion ( 2 ) connected to a crankshaft of an internal combustion engine by a toothed belt or a timing chain and has a hollow space ( 9 ) into which a winged wheel ( 13 ) is inserted and rotationally fixed to a camshaft of an internal combustion engine, the drive pinion ( 2 ) comprising on the inner surface of its circumferential wall ( 3 ) at least one working chamber ( 5 ), and the wings of the winged wheel ( 13 ) divide each working chamber ( 5 ) into two pressure chambers ( 10, 11 ) and to avoid pressure medium leakage between the pressure chambers ( 10, 11 ) of each working chamber ( 5 ) and between the individual working chambers ( 5 ), each wing of the winged wheel ( 13 ) is configured as a separate wing segment ( 18 ) which is displaceable within a guide ( 15 ) in the winged wheel ( 13 ) and is sealed leak-tight radially by the radial centrifugal force which results from the rotation of the vane-type adjusting device ( 1 ) during engine operation, and axially by at least one prestressed axial sealing element ( 23 ).

This application is a 371 of PCT/EP97/0619 filed Nov. 6, 1997.

FIELD OF THE INVENTION

The invention concerns an internal sealing of a camshaft-adjustingdevice in an internal combustion engine, particularly a vane-typeadjusting device comprising a drive pinion configured as an outer rotorwhich is connected to a crankshaft of an internal combustion engine by atoothed belt or a timing chain or by gears, said drive pinion comprisinga hollow space defined by a circumferential wall and two side walls, atoothing being provided on the outer surface of the circumferential walland at least one working chamber having limiting walls directed towardthe central longitudinal axis of the drive pinion being made in theinner surface of the circumferential wall, a winged wheel which has atleast one radial wing and is configured as an inner rotor rotationallyfixed to the camshaft being inserted into the hollow space of the drivepinion, wings of the winged wheel dividing each working chamber into twopressure chambers which, when pressurized successively or simultaneouslyby a pressure oil, effect a rotation and/or an infinitely variablehydraulic clamping of the camshaft relative to the crankshaft.

BACKGROUND OF THE INVENTION

In vane-type adjusting devices of the aforesaid type commonly known inthe art, the sealing of the pressure chambers in the hollow space of thedrive pinion against pressure oil leakage is generally effected on theone hand by two narrow radial gaps arranged between the wings of thewinged wheel and the circumferential wall and between the hub of thewinged wheel and the circumferential wall of the drive pinion, and onthe other hand by two narrow axial gaps between the side walls of thewings of the winged wheel and the side walls of the drive pinion. Fromthe manufacturing point of view, it is, however, not possible, orpossible only at very high expense, to make two narrow or sealing gapsin radial direction in such vane-type adjusting devices because thisresults in an overdetermination between the winged wheel and the drivepinion so that one of the radial gaps inevitably does not seal asintended. In spite of complicated manufacturing and a perfect fit of theindividual parts of such adjusting devices, increasing leakage of thepressure oil through the radial and axial gaps in excess of therestricted leakage required, per se, occurs with increasing temperatureof the pressure oil during engine operation. This leads to a reductionof the oil supply pressure and thus to retarded adjustment and a tooweak hydraulic clamping of the winged wheel and thus of the camshaft.This has a strong detrimental effect at high oil temperatures becausethe viscosity and the oil supply pressure are then particularly low sothat a frequent re-adjustment of the adjusting positions given by thecharacteristic diagram of engine timing is required and/or higher oilflow rates have to be provided for.

From another actuating device for a camshaft disclosed in DE-OS 39 22962, it is further known to make axial and radial grooves in the wingsof the winged wheel and arrange spring-mounted seals in these grooves tosealingly cooperate with the circumferential wall and the side walls ofthe hollow space of the drive pinion.

The manufacturing of vane-type adjusting devices with such sealingmeasures has proved to be very complicated and expensive, and, due tothe transition junctions between the individual axial and radial seals,these sealing measures cannot assure a satisfactory reduction of leakagevalues.

OBJECT OF THE INVENTION

It is therefore the object of the invention to conceive an internalsealing for a camshaft adjusting device of an internal combustionengine, particularly a vane-type adjusting device, with which undesiredpressure oil leakage between the pressure chambers in the hollow spaceof the drive pinion can be reduced to a minimum by simple andcost-effective means.

SUMMARY OF THE INVENTION

This object is achieved according to the invention in a vane-typeadjusting device by the fact that each wing of the winged wheel isconfigured as a separate wing segment which is displaceable within aguide in the winged wheel and exhibits a distance both radially from thecircumferential wall of the drive pinion in the respective workingchamber and axially from the side walls of the drive pinion, whichdistance is sealed leak-tight radially by the radial centrifugal forcewhich results from the rotation of the vane-type adjusting device duringengine operation and acts on the wing segment, and axially by least oneprestressed axial sealing element.

The vane-type adjusting device configured according to the inventionthus contrasts positively with the state of the art in that thefabrication of the winged wheel is substantially simplified and, at thesame time, the leakage values in the hollow space of the drive pinionare minimized to the greatest possible extent. It is true that thewinged wheel configured according to the invention comprises moreindividual elements than hitherto usual but these elements do not haveto be made to the close tolerances required in prior art vane-typeadjusting devices which have a disadvantageous effect on the time andcosts involved in the manufacturing of the vane-type adjusting device.Additionally, due to the inventive separation of the wings of the wingedwheel from the hub of the winged wheel, an overdetermination between thehub, the winged wheel and the drive pinion is no longer possible so thatan exact radial sealing gap can be obtained between the hub of thewinged wheel and the circumferential wall of the drive pinion.

In an advantageous embodiment of the invention, the guide for each wingsegment is made in the hub of the winged wheel preferably as a radialgroove which extends parallel to the central longitudinal axis, hasaxial side walls parallel to each other and surrounds the inserted,preferably cuboid wing segment approximately up to half of its height.The optimum solution with regard to achieving the desired angle ofadjustment between the crankshaft and the camshaft as well as therequired adjusting speed and hydraulic clamping force is to providethree such radial grooves uniformly spaced on the hub of the wingedwheel and arrange three identical wing segments in these radial grooves.The scope of protection of the invention, however, also extends toconfigurations in which the winged wheel has less than three or evenmore than three wing segments, and/or configurations in which the wingsegments are surrounded by the radial grooves to a higher or even alower level than half their height. Similarly, the preferred cuboidconfiguration of the wing segments is only one of several possibleshapes because with such wing segments, it is possible to achieve arelatively long radial sealing gap and thus a high degree ofleak-tightness between the pressure chambers in each working chamber.

According to a further feature of the invention, the sealing surface ofeach wing segment cooperating with the circumferential wall of the drivepinion in each working chamber therefore preferably has in radialdirection, the same radius and in axial direction, the same surfacecontour as the circumferential wall in each working chamber. Incontrast, the bottom surface of each wing segment situated opposite thissealing surface, which may also have a smaller radius, preferably has astraight configuration, so that the wing segment, at the same time,possesses good sliding properties within the working chamber during theadjusting operation, and a canting or tilting of the wing segmentswithin the guides is substantially excluded. Pressure medium leakagethrough the gaps formed on a side wall of the guide and/or under thebottom surface of the wing segments due to the radial movability of thewing segments is likewise substantially excluded because the pressure ofthe pressure medium prevailing in a pressure chamber at any time islikewise present in these gaps. As is the case with steel sealing rings,this pressure effects, on the one hand, that the wing segments aresealingly pressed against the side wall of the guide opposing thedirection of pressure and on the other hand, the radial centrifugalforce of the wing segments is assisted by a radial pressure force whichenhances the sealing action of the wing segments on the circumferentialwall in the working chambers. In addition, it is also possible tofurther assist the radial centrifugal force of the wing segments byproviding spring elements such as bent girders, compression springs orthe like which act radially on the bottom surface of the wing segmentsto further intensify the sealing action thereof.

Finally, according to a further feature of the inventive sealing of avane-type adjusting device, the axial sealing elements on each wingsegment are made as steel sealing strips arranged in axial groovesextending over their entire height. These steel sealing strips areprestressed by spring elements such as compression springs, leaf springsor elastomer elements acting on their groove-proximate longitudinaledges. A satisfactory sealing action between the pressure chambers inaxial direction is obtained already by arranging a steel sealing striponly on one of the axial ends of the wing segments in such an axialgroove but it is also possible to arrange one or more steel sealingstrips on both axial ends of each wing segment to cooperate with theside walls of the drive pinion or, instead, to use sealing strips madeof a plastic material, rubber or non-ferrous materials. The steelsealing strips preferably have a square cross-section whose widthcorresponds approximately to the width of the complementary axial grooveand whose height, if compression springs are used for pre-stressingthem, is slightly larger than the depth of the axial groove. If only onesteel sealing strip is arranged on each wing segment, the compressionsprings are disposed in pocket bores starting from the groove bottom ofthe axial groove. However, the most advantageous solution is to providetwo compression springs and two pocket bores for each steel sealingstrip. When using two steel sealing strips for each wing segment, thecompression springs are arranged in through-bores extending from groovebottom to groove bottom so that the steel sealing strips of each wingsegment support each other. If the prestress of the steel sealing stripsis produced by using leaf springs or elastomer elements instead ofcompression springs, the depth of the axial groove has to be increasedby the height of the leaf springs or elastomer elements if these extendcontinuously over the entire length of the axial groove. In contrast,pointwise acting elastomer elements can be arranged in the wing segmentsof the winged wheel in the same manner as compression springs. It is,however, also possible to configure the axial sealing elements assealing strips with a circular or other suitable profile cross-sectionand/or to arrange the axial sealing elements in the axial grooveswithout prestress and realize the pressing function of the springelements in the same manner as when steel sealing rings are used, i.e.through the pressure of the hydraulic pressure medium.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described more closely in the following with referenceto the drawings in which:

FIG. 1 shows a longitudinal section through a vane-type adjusting devicehaving a sealing according to the invention;

FIG. 2 shows a section taken along line A—A of FIG. 1;

FIG. 3 shows a section taken along line B—B of FIG. 2;

FIG. 4 shows the detail Z of FIG. 1 with the use of elastomer elements.

DETAILED DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 show different views of a vane-type adjusting device whichcomprises in a known manner, a drive pinion 2 configured as an outerrotor and a winged wheel 13 configured as an inner rotor. The drawingsdo not show that in the present case, the drive pinion 2 is connected toa crankshaft of an internal combustion engine by a timing chain and thewinged wheel 13 is rotationally fixed on a camshaft of an internalcombustion engine. It can be seen in the drawings that the drive pinion2 comprises a hollow space 9 defined by a circumferential wall 3 and twoside walls 7, 8, there being provided on the outer surface of thecircumferential wall 3, a toothing 4 and on the inner surface of thecircumferential wall 3, three working chambers 5 each of which haslimiting walls 6 a, 6 b directed towards the central longitudinal axisof the drive pinion 2. The winged wheel 13, which in the present case isconfigured with three radial wings, is inserted into this hollow space 9of the drive pinion 2, and the wings of the winged wheel 13 divide eachworking chamber 5 into two pressure chambers 10, 11 which, whenpressurized successively or simultaneously by a pressure oil, effect arotation and/or an infinitely variable clamping of the camshaft relativeto the crankshaft.

To avoid pressure medium leakage between the pressure chambers 10, 11 inthe working chambers 5, each wing of the winged wheel 13, as can be seenin FIG. 2, is configured according to the invention as a separate wingsegment 18 which is displaceable in a guide 15 in the winged wheel 13and, during a standstill of the vane-type adjusting device 1, said wingsegment 18 exhibits a distance both radially from the circumferentialwall 3 of the drive pinion 2 within the respective working chamber 5 andaxially from the side walls 7, 8 of the drive pinion 2. This distance,not referenced in the drawings, is sealed leak-tight, as schematicallyindicated in FIG. 2, radially by the radial centrifugal force whichresults during the operation of the engine from the rotation of thevane-type adjusting device 1 and acts on the wing segment 18, andaxially, as can be seen in FIG. 3, by a prestressed axial sealingelement 23.

It can be further seen in FIG. 2 that the guide 15 for each wing segment18 is made in the hub 14 of the winged wheel 13 as a radial grooveextending parallel to the central longitudinal axis and having axialside walls 16, 17 parallel to each other. Corresponding to the number ofwings of the winged wheel 13, three such radial grooves are arrangedequally spaced on the hub 14 of the winged wheel 18 (13). A cuboid wingsegment 18 is arranged in each of these radial grooves so as to besurrounded approximately up to half of its height by the guide 15. Thesealing surface 19 of each wing segment 18 cooperating with thecircumferential wall 3 of the drive pinion 3 of each working chamber 5has in radial direction, the same radius and in axial direction, thesame surface contour as the circumferential wall 3 in each workingchamber 5 so as to exclude tilting or canting of the wing segments 18within the guides 15 and create relatively long radial sealing gapsbetween the pressure chambers 10, 11 in each working chamber 5. Sealingbetween the individual working chambers 5 in the circumferential wall 3of the drive pinion 2 relative to each other is further achieved by thesealing gaps situated between the hub 14 of the winged wheel 13 and thecircumferential wall 3 of the drive pinion 2 and identified in FIG. 2 bythe reference numeral 12.

FIG. 3 further shows that the axial sealing elements 23 on each wingsegment 18 are configured as steel sealing strips and arranged in axialgrooves 22 extending on their axial end 21 over their entire height. Thesteel sealing strips have a square cross section with a widthcorresponding approximately to the width of the axial groove 22 and aheight which is slightly larger than the depth of the axial groove 22.Two compression springs 25 acting pointwise on the groove-proximatelongitudinal edges 24 of the steel sealing strips are arranged in pocketbores, not referenced, starting from the groove bottom of the axialgroove 22. These compression springs 25 produce a prestress on the axialsealing elements so that the pressure chambers 10, 11 in each workingchamber 5 are also sealed from each other in axial direction.Alternatively, the prestress on the axial sealing elements may also beproduced, as shown in FIG. 4, by replacing the compression springs 25 ofthe steel sealing strips by elastomer elements 26 which are arranged inaxial grooves 22 of adequate depth and which act linearly on thegroove-proximate longitudinal edges 24 of the axial sealing elements 23.

What is claimed is:
 1. Camshaft adjusting device for an internalcombustion engine, including a vane-type adjusting device comprising adrive pinion (2) configured as an outer rotor which is connected to acrankshaft of an internal combustion engine by a toothed belt or atiming chain or by gears, said drive pinion (2) comprising a hollowspace (9) defined by a circumferential wall (3) and two side walls (7,8), a toothing (4) being provided on the outer surface of thecircumferential wall (3) and at least one working chamber (5) havinglimiting walls (6 a, 6 b) directed toward the central longitudinal axisof the drive pinion (2) being made in the inner surface of thecircumferential wall (3), a winged wheel (13) which has at least oneradial wing and is configured as an inner rotor rotationally fixed to acamshaft being inserted into the hollow space (9) of the drive pinion(2), wings of the winged wheel (13) dividing each working chamber (5)into two pressure chambers (10, 11) which, when pressurized successivelyor simultaneously by a pressure oil, effect a rotation and/or aninfinitely variable hydraulic clamping of the camshaft relative to thecrankshaft, characterized in that each wing of the winged wheel (13) isconfigured as a separate wing segment (18) which is displaceable withina guide (15) in the winged wheel (13) and exhibits a distance bothradially from the circumferential wall (3) of the drive pinion (2) inthe respective working chamber (5) and axially from the side walls (7,8) of the drive pinion (2), which distance is sealed leak-tight radiallyby a sealing gap (12) between the end sealing surface (19) of the wingsegment (18) and the circumferential wall (3) of the drive pinion (2),which sealing gap narrows under the action of centrifugal force duringrotation of the vane-type adjusting device, and said distance is sealedaxially by least one prestressed axial sealing element (23) arranged onan axial end (20 or 21) of the wing segment (18).
 2. Camshaft adjustingdevice according to claim 1, characterized in that the guide (15) foreach wing segment (18) is made in the hub (14) of the winged wheel (13)as an axial groove which extends parallel to the central longitudinalaxis, has lateral surfaces (16, 17) parallel to each other and surroundsthe inserted wing segment (18) approximately up to half of its height.3. Camshaft adjusting device according to claim 1, characterized in thatthe end sealing surface (19) of each wing segment (18) has in radialdirection, the same radius and in axial direction, the same surfacecontour as the circumferential wall (3) of the drive pinion (2) in therespective working chamber (5).
 4. Camshaft adjusting device accordingto claim 1, characterized in that the axial sealing elements (23)arranged on at least one axial end (20 or 21) of each wing segment (18)are configured as steel sealing strips which are arranged in radialgrooves (22) extending over the entire height of the wing segments (18)in the respective axial end (20, 21), said axial sealing elements (23)being prestressed by spring elements including compression springs (25)and elastomer elements (26), acting on their groove-proximatelongitudinal edge (24).